How do I configure a rule in ICC that would be "equal to" but not case sensitive?

An advanced rule is being used to determine the extension of the document being processed by the task route. The rule is configured as follows: Contains( . {".pdf", ".tiff", ".txt", ".doc", ".PDF"}) The issue is, how to validate the file extension, without having every possible combination of upper and lower case letters listed in the array. For example, some documents have the extension of: .PdF.

How would the rule be configured to validate the file extensions regardless of its case?

Would some other expression prototype be used instead? Can you configure a regexp within the Contains?